Remember: Just because "it" is on the internet, it doesn't mean that content, images, audio, videos, etc are "up for grabs" to incorporate into your own work and pass off as your own. Visit http://creativecommons.org/ home page to find out more about Creative Commons, a licensing system that gives creators a simple, standardized way to copyright their material while granting permission to use, copy, tweak, or build upon their work, commercially or non-commercially, as they wish. As a user, by noting the Creative Commons "stamp" on the work, you will know how you can use that work without having to write for permission (unless you want to use it differently than the CC permission allows). A great system for taking out the guesswork and the hassle of getting permission as well as a way to keep us users from being limited to public domain work only!
For example, the Creative Commons site has this license on the bottom of the page which allows me to post this info on the tech wiki page:
The Licenses
Attribution CC BY
This license lets others distribute, remix, tweak, and build upon your work, even commercially, as long as they credit you for the original creation. This is the most accommodating of licenses offered. Recommended for maximum dissemination and use of licensed materials.
This license lets others remix, tweak, and build upon your work even for commercial purposes, as long as they credit you and license their new creations under the identical terms. This license is often compared to “copyleft” free and open source software licenses. All new works based on yours will carry the same license, so any derivatives will also allow commercial use. This is the license used by Wikipedia, and is recommended for materials that would benefit from incorporating content from Wikipedia and similarly licensed projects.
This license lets others remix, tweak, and build upon your work non-commercially, and although their new works must also acknowledge you and be non-commercial, they don’t have to license their derivative works on the same terms.
This license lets others remix, tweak, and build upon your work non-commercially, as long as they credit you and license their new creations under the identical terms.
This license is the most restrictive of our six main licenses, only allowing others to download your works and share them with others as long as they credit you, but they can’t change them in any way or use them commercially.
We also provide tools that work in the “all rights granted” space of the public domain. Our CC0 tool allows licensors to waive all rights and place a work in the public domain, and our Public Domain Mark allows any web user to “mark” a work as being in the public domain.
For example, the Creative Commons site has this license on the bottom of the page which allows me to post this info on the tech wiki page:
The Licenses
Attribution CC BY
Attribution-ShareAlike CC BY-SA
Attribution-NoDerivs CC BY-ND
Attribution-NonCommercial CC BY-NC
Attribution-NonCommercial-ShareAlike CC BY-NC-SA
Attribution-NonCommercial-NoDerivs CC BY-NC-ND
We also provide tools that work in the “all rights granted” space of the public domain. Our CC0 tool allows licensors to waive all rights and place a work in the public domain, and our Public Domain Mark allows any web user to “mark” a work as being in the public domain.